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Pre-Assembly Parts Compatibility Review


carbon9

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Hi, this will be my first AR-308 build and knowing there may be possible combinations which do not play well together I am appealing to you, the experienced, for critiques or suggestions before I start assembly.  I have everything on my list except the barrel which should come back any day now.

Thank you.

This build will be simply for fun and maybe minor Heavy Metal Competition.

Sun Devil Billet Upper and Lower

Criterion 20" M118 SS (1-12) barrel sent off to ADCO for reprofiling and cutting. .825 under the handguard and .750 from gas block forward, cut, threaded and crowned for a barrel length of 16.75" w/rifle length gas

Firebird Precision LoPro SS Gas Block, the only gas block I know of designed to mount directly against the gas block shoulder(ingenius), Syrac  or JP A2 style adjustable gas block/sight for a dissipator style build.

SJC Titan comp

Carbon Arms AR-308 15" Carbon Fiber handguard w/barrel nut

JP LMOS .308 complete carrier

BCM 4 .308 charging handle

JP SCS buffer/spring-Silent Captured Spring

SR Gold Trigger

Magpul UBR Stock and MIAD

I am still trying to figure out which safety I am going to run as I need it to go back on safe with minimal effort when dumping the gun.

Thank you again for your input.

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Hi, this will be my first AR-308 build and knowing there may be possible combinations which do not play well together I am appealing to you, the experienced, for critiques or suggestions before I start assembly.  I have everything on my list except the barrel which should come back any day now.

Thank you.

This build will be simply for fun and maybe minor Heavy Metal Competition.

Sun Devil Billet Upper and Lower

Criterion 20" M118 SS (1-12) barrel sent off to ADCO for reprofiling and cutting. .825 under the handguard and .750 from gas block forward, cut, threaded and crowned for a barrel length of 16.75" w/rifle length gas

Firebird Precision LoPro SS Gas Block, the only gas block I know of designed to mount directly against the gas block shoulder(ingenius), Syrac  or JP A2 style adjustable gas block/sight for a dissipator style build.

SJC Titan comp

Carbon Arms AR-308 15" Carbon Fiber handguard w/barrel nut

JP LMOS .308 complete carrier

BCM 4 .308 charging handle

JP SCS buffer/spring-Silent Captured Spring

SR Gold Trigger

Magpul UBR Stock and MIAD

I am still trying to figure out which safety I am going to run as I need it to go back on safe with minimal effort when dumping the gun.

Thank you again for your input.

I think all of the ones I have put on , butt right up to the shoulder . I'm sure there are some out there that don't though.

B.A.D . safeties

Interesting barrel modifications.

There are people that say a 16" bbl. & rifle length gas system won't work . Strange , mine works . <munch>

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survivalshop. 

I was under the impression most gas blocks needed .030" space from the shoulder to allow the old non-freefloat/delta handguard mount, an antiquated idea in my opinion.  When was the last time you really saw or kept a non free float handguard?  I like the BAD safeties but have seen so many fitment issues with the SR Gold in what little research I have done.  Maybe I will try one after all, I'll give them a call tomorrow.  I went with the 16.75" barrel length to allow any front iron sight combo I may wish to run in the future for 400yd and less courses.  Had to keep the rifle length gas and I wanted the 1-12 twist for all the 110gr and 125gr bullets I will be using for Heavy Metal.  I did hear Fulton Armory is working on another 16" .308 Criterion barrel in a lightweight profile, not sure of the gas length or twist, couldn't wait that long :D.  Yes, I am envious of your 16" barrel ;D

MikedaddyH.

Any firm ETA on the SD side charging upper?  That is something I would really like to see first.  I'm sure Dave would let me exchange my upper towards the new one if I haven't built it yet.  Of course, my lack of patience will probably force me to build one of each.

Thank you for all the info and guidance. 

Also, has anybody owned and/or used a UBR and an ACS-L at the same time?  What is the cheek weld difference or similarity between the two?  I run UBRs and a PRS on my ARs .  I actually like the UBRs best but am thinking a UBR with the JP SCS might be a little buttstock heavy and an ACS-L with the JP SCS might give me the same weight as a UBR with standard spring and buffer.  Technically, I should just run the UBR I already have and see how it goes.

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News Flash, really? Funny, I've always dealt directly with Dave on the SD-15 receiver sets I have bought and built in the past.  But then I do see how an engineer/designer/machinist who still helps with his father's/family business would have somebody good with books and people run the front.  I see him and Anita fairly often as they live a few doors down from my mother so I am sure either one of them will help me out with the exchange or additional purchase.  I was hoping you would be more knowledgeable and have an actual ETA on the side charging upper so I wouldn't have to bug Dave with how busy he is.  Thank you anyways for your help.

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survivalshop. 

I was under the impression most gas blocks needed .030" space from the shoulder to allow the old non-freefloat/delta handguard mount, an antiquated idea in my opinion.  When was the last time you really saw or kept a non free float handguard?  I like the BAD safeties but have seen so many fitment issues with the SR Gold in what little research I have done.  Maybe I will try one after all, I'll give them a call tomorrow.  I went with the 16.75" barrel length to allow any front iron sight combo I may wish to run in the future for 400yd and less courses.  Had to keep the rifle length gas and I wanted the 1-12 twist for all the 110gr and 125gr bullets I will be using for Heavy Metal.  I did hear Fulton Armory is working on another 16" .308 Criterion barrel in a lightweight profile, not sure of the gas length or twist, couldn't wait that long :D.  Yes, I am envious of your 16" barrel ;D

MikedaddyH.

Any firm ETA on the SD side charging upper?  That is something I would really like to see first.  I'm sure Dave would let me exchange my upper towards the new one if I haven't built it yet.  Of course, my lack of patience will probably force me to build one of each.

Thank you for all the info and guidance. 

Also, has anybody owned and/or used a UBR and an ACS-L at the same time?  What is the cheek weld difference or similarity between the two?  I run UBRs and a PRS on my ARs .  I actually like the UBRs best but am thinking a UBR with the JP SCS might be a little buttstock heavy and an ACS-L with the JP SCS might give me the same weight as a UBR with standard spring and buffer.  Technically, I should just run the UBR I already have and see how it goes.

It is my experience that most gas blocks ( non A2 front sight types ) do not allow for the spacing for the A2 hand guard end cap .

I measure all the gas blocks I install for gas port placement & if you take it for granted that you can adj. them for that gap , you may be partially blocking the barrels gas port , which may hinder rifle action function .

A proper size drill bit & a dial caliper to measure the distance from the drill bit to the shoulder & same for the gas block , measure from the shoulder seating end ,to the drill bit placed into the gas port of the gas block & you will know if you can leave that gap or not .

Most gas block ports are larger in dia. than there corresponding port in the barrel & may be able to work with out any function problems , but you never know .

Range reports please.

I do like my 16" 308 , just too busy with every one elses rifles to enjoy her enough .

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My barrel returned from ADCO today, amazingly quick, great service and nice work.  The barrel left weighing 3.55lbs and came back weighing 2.582lbs.  The Titan comp, Syrac gas block, gas tube, barrel and 15" Carbon Fiber handguard weigh 3.83lbs combined.  Not super light but very manageable.  Now to find time to build it.....

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  • 2 weeks later...

Went to Quentin Defense and looked at the slick side 308 upper and it is in production now ! This fits the Sun Devil Lower receiver and the DPMS lower receiver, has extra beveling around the charging handle mouth area. <thumbsup>

The side charging 308 upper is still in the R & D stage with the prototype.

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